Semiconductor device

ABSTRACT

A semiconductor device where an outside connection terminal of a semiconductor element and an electrode of a wiring board are connected to each other via a conductive adhesive, the conductive adhesive includes a first conductive adhesive; and a second conductive adhesive covering the first conductive adhesive; wherein the first conductive adhesive contains a conductive filler including silver (Ag); and the second conductive adhesive contains a conductive filler including a metal selected from a group consisting of tin (Sn), zinc (Zn), cobalt (Co), iron (Fe), palladium (Pd), and platinum (Pt).

This application is a divisional of application Ser. No. 12/038,444,Feb. 27, 2008.

TECHNICAL FIELD

The present invention generally relates to semiconductor devices andmanufacturing methods of the semiconductor devices.

BACKGROUND

As electronic devices such as mobile phones or digital cameras have highfunctionality and small sizes, higher functions and higher integrationare in demand for semiconductor devices provided in the electronicdevices. Accordingly, recently, a semiconductor element such as aintegrated circuit chip being directly mounted on a wiring board hasbeen suggested so that the mounting area is made small and efficient useis achieved.

More specifically, in the semiconductor device, a semiconductorintegrated circuit element (hereinafter “semiconductor element”) ismounted on a wiring board by using convex (projection) outsideconnection terminals called wire bumps. Insulating resin such as glassepoxy resin is used for a base part of the wiring board. Conductivelayers made of copper (Cu) or the like are selectively provided on amain surface of the wiring board. The convex (projection) outsideconnection terminals provided on a main surface of the semiconductorelement are connected to the conductive layers of the wiring board.Outside connection terminals such as spherical electrode terminals areprovided on surfaces of electrodes selectively formed on another mainsurface of the wiring board. In the above-mentioned semiconductordevice, the semiconductor element is mounted on the wiring board in aso-called flip-chip (face-down) state. The above-mentioned flip-chipmounting structure is formed by the following methods.

In a first method, when a semiconductor element is mounted on a wiringboard, an underfill material such as a thermosetting adhesive issupplied on a main surface of the wiring board in advance. While thesemiconductor element is mounted on the wiring board via the underfillby applying high loads so that the underfill material is spread, theunderfill material is made to flow across in the entire surface area ofthe semiconductor element by capillary action. At the same time, theunderfill material is cured by heat applied at the time when thesemiconductor element is mounted.

In the first method, since the high loads are applied to thesemiconductor at the same time that the underfill material is cured, theconvex shaped outside connection terminal of the semiconductor elementand the electrode of the wiring board are crushed against each other soas to be connected to each other.

In this pressure connecting type first method, connection of the convexshaped outside connection terminal of the semiconductor element and theelectrode of the wiring board is maintained by using a contractive forcefor curing the underfill material by heat and a repulsive force when theconvex shaped outside connection terminal of the semiconductor elementis crushed, so as to make electric connection between the convex shapedoutside connection terminal of the semiconductor element and theelectrode of the wiring board.

In a second method, a conductive adhesive made of, for example, silver(Ag) paste is transferred to the head end of the convex shaped outsideconnection terminal. The convex shaped outside connection terminal ofthe semiconductor device and the electrode of the wiring board areconnected to each other via the conductive adhesive. Then, an underfillmaterial is applied in the vicinity of the external circumference of thesemiconductor element on the wiring board. The underfill material ismade to flow across the entire surface area of the semiconductor elementby capillary action and is cured by heating.

It is general practice to use, as the above-mentioned conductiveadhesive, silver (Ag) or a mixture or an alloy containing silver (Ag) asa main ingredient. Silver (Ag) has a low volume resistivity and lowcontact resistance with gold (Au) forming the convex shaped outsideconnection terminal of the semiconductor element.

Japanese Patent No. 3409957 describes an example where two kinds ofconductive adhesives are used for a connecting part of an electrode of awiring board and an electrode of a semiconductor element. Morespecifically, a structure of a projection electrode of an IC chipmounted on the wiring board in a face-down manner is suggested inJapanese Patent No. 3409957. A first conductive adhesive made of aconductive filler of silver palladium (AgPd) is transferred to theprojection electrode and a second conductive adhesive made of aconductive filler of silver (Ag) is transferred to the outside of thefirst conductive adhesive. A thin semiconductor device having goodelectric properties can be easily formed by flip chip mounting usingsuch a method.

However, as the semiconductor device has high level functions, the pitchof the convex shaped outside connection terminals becomes narrow so thatthe size of the convex shaped outside connection terminals become small.

In this pressure connecting type first method, high loads are applied tothe semiconductor element at the same time when the underfill materialis cured so that the convex shaped outside connection terminal of thesemiconductor element is crushed. However, since the semiconductorelement is more solid than the wiring board, a curve whose top part issituated substantially in the center of the wiring board may be formedin the wiring board where the semiconductor element is flip-chipmounted. As a result of this, a gap in a vertical direction between thesemiconductor element and the wiring board becomes narrow in an areaother than an area where electric connection of the semiconductorelement and the wiring board is formed by the electrode and the convexshaped outside connection terminal becomes narrow.

Because of this, a particle generated during a manufacturing process ofthe semiconductor device enters in the underfill material positioned inthe gap in the vertical direction between the semiconductor element andthe wiring board so that a circuit of the semiconductor element may bebroken.

If the load applied when the semiconductor element and the wiring boardare connected to each other so that the gap in the vertical directionbetween the semiconductor element and the wiring board is made wide, aforce for connecting the convex shaped outside connection terminal ofthe semiconductor device and the electrode of the wiring board may bedegraded so that shorts between the semiconductor element and the wiringboard may be generated. In other words, if the pressure connecting typefirst method is applied to flip chip mounting of the semiconductorelement where the convex shaped outside connection terminals are formedwith a narrow pitch on the wiring board, a connection limit may begenerated where the connection between the semiconductor element and thewiring board is released.

In addition, in a case where a test having a heat history such as areflow test or a temperature cycle test is performed, due to stresscaused by thermal expansion based on differences of thermal expansioncoefficients of the semiconductor elements, the wiring board, theunderfill material, the conductive adhesive, and others, the connectionof the semiconductor element and the wiring board may become loose and ashort between the semiconductor element and the wiring board may begenerated.

In the above-discussed second method, the semiconductor element, wherethe conductive adhesive of silver (Ag) paste is transferred on the headend of the convex shaped outside connection terminal, is mounted on thewiring board so that the convex shaped outside connection terminal ofthe semiconductor element and the electrode of the wiring board areconnected to each other. Accordingly, a connection part where the convexshaped outside connection terminal of the semiconductor element and theelectrode of the wiring board are connected to each other is a lowelasticity body.

Accordingly, in a case where the test having a heat history such as areflow test or a temperature cycle test is performed, although theconnection between the semiconductor element and the wing board is notloosened, ion migration, where silver (Ag) contained in the conductiveadhesive is ionized due to an electric field or environment and elutedin the periphery, may be easily generated. In particular, if the pitchof the convex shaped outside connection terminals becomes narrow and alarge amount of silver (Ag) exists in the connection part where theconvex shaped outside connection terminals of the semiconductor elementand the electrodes of the wiring board are connected to each other, theshorts due to the ion migration between the semiconductor element andthe wiring board may be easily generated.

Furthermore, in the example discussed in Japanese Patent No. 3409957,since the second conductive adhesive made of silver (Ag) conductivefiller is formed on the outermost circumferential part of the projectionelectrodes, it is difficult to avoid generation of the above-mentionedsilver ion migration.

SUMMARY

One aspect of the present invention may be to provide a semiconductordevice where an outside connection terminal of a semiconductor elementand an electrode of a wiring board are connected to each other via aconductive adhesive, the conductive adhesive including a firstconductive adhesive; and a second conductive adhesive covering the firstconductive adhesive; wherein the first conductive adhesive contains aconductive filler including silver (Ag); and the second conductiveadhesive contains a conductive filler including a metal selected from agroup consisting of tin (Sn), zinc (Zn), cobalt (Co), iron (Fe),palladium (Pd), and platinum (Pt).

Another aspect of the present invention may be to provide amanufacturing method of a semiconductor device, the semiconductor deviceincluding an outside connection terminal of a semiconductor element andan electrode of a wiring board that are connected to each other via aconductive adhesive, the manufacturing method including a step offorming a first conductive adhesive containing a conductive fillerincluding silver (Ag) on the outside connection terminal of thesemiconductor element; a step of forming a second conductive adhesive ona surface of the first conductive adhesive, the second conductiveadhesive containing a conductive filler including a metal selected froma group consisting of tin (Sn), zinc (Zn), cobalt (Co), iron (Fe),palladium (Pd), and platinum (Pt); and a step of connecting the outsideconnection terminal of the semiconductor element to the electrode formedon the wiring board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a semiconductor device of anembodiment of the present invention;

FIG. 2 is an expanded view of a part surrounded by a dotted line A ofFIG. 1;

FIG. 3 is a view of a conductive adhesive (shown in FIG. 2) seen from anupper surface side of a bonding electrode;

FIG. 4 is a first view of a first manufacturing method of thesemiconductor device of the embodiment of the present invention;

FIG. 5 is a second view of the first manufacturing method of thesemiconductor device of the embodiment of the present invention;

FIG. 6 is a third view of the first manufacturing method of thesemiconductor device of the embodiment of the present invention;

FIG. 7 is a fourth view of the first manufacturing method of thesemiconductor device of the embodiment of the present invention;

FIG. 8 is a first view of a second manufacturing method of thesemiconductor device of the embodiment of the present invention;

FIG. 9 is a second view of the second manufacturing method of thesemiconductor device of the embodiment of the present invention; and

FIG. 10 is a third view of the second manufacturing method of thesemiconductor device of the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A description is given below, with reference to the FIG. 1 through FIG.10 of embodiments of the present invention.

For the convenience of explanation, a structure of a semiconductordevice of an embodiment of the present invention is discussed and then amanufacturing method of the semiconductor device is discussed.

[Semiconductor Device]

FIG. 1 is a cross-sectional view of a semiconductor device of anembodiment of the present invention.

Referring to FIG. 1, in a semiconductor device 10, a semiconductorintegrated circuit element (hereinafter “semiconductor element”) 12 ismounted and fixed on one of main surfaces of a wiring board 11 in aso-called flip-chip (face-down) state.

The wiring board 11 is made of an organic resin material such asglass-epoxy, glass-BT (bismaleimide-triazine), or polyimide, or aninorganic material such as ceramic or glass. The wiring pattern notshown in FIG. 1 and made of copper (Cu) or the like is selectivelyprovided on the wiring board 11. The wiring board 11 may be called aninterposer or a supporting board.

Bonding electrodes 14, where the convex (projection) shaped outsideconnection terminals 13 of the semiconductor element 12 mounted on thewiring board 11 are connected, are formed on the main surface of thewiring board 11 where the semiconductor element 12 is mounted. Thebonding electrode 14 is made of, for example, copper (Cu), nickel (Ni),or gold (Au).

A conductive layer not shown in FIG. 1 is provided on another mainsurface of the wiring board 11 situated at a side opposite to thesurface where the semiconductor element 12 is mounted. Plural outsideconnection terminals 15 such as spherical shaped electrode terminalsmade of solder or the like are provided on the conductive layer in agrid pattern.

The semiconductor element 12 includes a silicon (Si) semiconductorsubstrate and is formed by a known semiconductor manufacturing process.The present invention can be applied to a semiconductor device having asemiconductor element made of a chemical semiconductor such as galliumarsenide (GaAs).

Outside connection terminal pads 16 are selectively provided in a lineon the main surface of the semiconductor substrate 12. For example, theoutside connection terminal pads 16 are provided along four side in thevicinity of the four sides of the main surface of the semiconductorsubstrate 12 or along two sides in the vicinity of the two sides facingeach other of the main surface of the semiconductor substrate 12. Theconvex (projection) shaped outside connection terminals 13 called wirebumps are provided on the outside connection terminal pads 16.

The outside connection terminal pads 16 are made of aluminum (Al),copper (Cu), or an alloy of these metals. A gold (Au) layer may beformed on an exposed surface (top layer) of the outside connectionterminal pads 16 by an electrolytic plating method, a vapor depositionmethod, or the like.

In addition, the convex (projection) shaped outside connection terminal13 provided on each of the outside connection terminal pads 16 is formedby, for example, a so-called ball bonding method using a wire bondingtechnique. More specifically, a seating part is formed by pressurefixing or connecting a gold (Au) ball and a projection part projectingfrom the seating part so that the convex (projection) shaped outsideconnection terminal 13 is formed.

The convex (projection) shaped outside connection terminal 13 is notlimited to the above-mentioned example. For example, the convex(projection) shaped outside connection terminal 13 may be made of copper(Cu), an alloy of copper (Cu) and gold (Au), solder, or the like.

As discussed above, while the convex shaped outside connection terminal13 of the semiconductor element 12 are connected to the correspondingbonding electrodes 14 of the wiring board 11, the conductive adhesive 20is provided on the convex shaped outside connection terminals 13. Atleast the projection parts of the convex shaped outside connectionterminals 13 of the semiconductor element 12 and the bonding electrodes14 corresponding to these are commonly covered with the conductiveadhesive 20 so that the convex shaped outside connection terminals 13and the bonding electrodes 14 are mechanically and electricallyconnected to each other.

Here, an arrangement structure of the conductive adhesive 20 isdiscussed with reference to FIG. 2. FIG. 2 is an expanded view of a partsurrounded by a dotted line A of FIG. 1.

As shown in FIG. 2, the conductive adhesive 20 has a two-layer structureformed by a first conductive adhesive 20-1 and a second conductiveadhesive 20-2. More specifically, a layer made of the first conductiveadhesive 20-1 is provided around a projection part 13-b positioned on aseating part 13-a of the convex shaped outside connection terminal 13.The second conductive adhesive 20-2 is formed outside the firstconductive adhesive 20-1 so as to cover the external surface of thefirst conductive adhesive 20-1.

The first conductive adhesive 20-1 and the second conductive adhesive20-2 are adhesives containing metal particles as conductive fillers thatare dispersed in binder resin and an organic solvent. As the binderresin, examples include an epoxy composition, an acrylic composition, avinyl composition, a thermosetting composition such as a compositionwhere a hydroxyl group is provided at an end, a resin compositionsoluble in a solvent, a mixture of them, or the like. In the epoxy resinas the binder resin, an epoxy based compound as epoxy curing agent is anessential ingredient and a surface active agent or flux may be applied.

As the first conductive adhesive 20-1, an adhesive may be used wheresilver (Ag) or a mixture (intermetallic compound) or an alloy whose mainingredient is silver (Ag) is dispersed as a conductive filler in theabove-mentioned binder resin. Silver (Ag) has a low volume resistivityand low contact resistance with gold (Au) forming the convex shapedoutside connection terminal 13 of the semiconductor element 12. Silverpalladium (AgPd), for example, can be used as a mixture (intermetalliccompound) or alloy whose main ingredient is silver (Ag). For example, anadhesive where 30 wt % or more of silver (Ag) particles having 1 μm orless of an average grain diameter are dispersed in the binder resin canbe used as the first conductive adhesive 20-1.

As the second conductive adhesive 20-2, an adhesive can be used wheretin (Sn) or mixture (intermetallic compound) or an alloy whose mainingredient is tin (Sn) is dispersed as a conductive filler in theabove-mentioned binder resin. For example, an adhesive where 30 wt % ormore of tin (Sn) particles having 0.1 μm or less average grain diameterare dispersed in the binder resin can be used as the second conductiveadhesive 20-2.

Since in the second conductive adhesive 20-2, an adhesive where tin (Sn)or a mixture (intermetallic compound) or an alloy whose main ingredientis tin (Sn) is dispersed as a conductive filler in the above-mentionedbinder resin, due to heat applied when the convex shaped outsideconnection terminals 13 of the semiconductor element 12 are connected tothe bonding electrodes 14 of the wiring board 11, the second conductiveadhesive 20-2 takes oxygen (O₂) in from the environment so that a thinoxide film is formed on an external surface of the second conductiveadhesive 20-2.

In other words, the conductive adhesive 20 configured to connect theconvex shaped outside connection terminals 13 of the semiconductorelement 12 and the bonding electrodes 14 of the wiring board 11 has atwo-layer structure formed by the first conductive adhesive 20-1 and thesecond conductive adhesive 20-2. Accordingly, even if silver (Ag) orsilver contained in the mixture (intermetallic compound) or an alloywhose main ingredient is silver (Ag) is eluted as ions, by the oxidefilm of tin (Sn) formed on the external surface of the second conductiveadhesive 20-2, it is possible to prevent hydroxide ions (OH⁻) suppliedfrom the wiring board 11 or the underfill material 17 from being takeninto the first conductive adhesive 20-1 too much.

Accordingly, in this example, as compared to a case such as thatdiscussed in Japanese Patent No. 3409957, where silver (Ag) is formed onthe outermost external circumferential part of the convex shaped outsideconnection terminal of the semiconductor element, it is possible toreduce ratios of a case where silver ions (Ag⁺) and hydroxide ions (OH⁻)are associated with each other. Hence, it is possible to preventdendrite formation causing the ion migration and prevent shorts betweenthe semiconductor element 12 and the wiring board 11 due to ionmigration of silver (Ag).

In the above-discussed example, an adhesive where tin (Sn) or a mixture(intermetallic compound) or an alloy whose main ingredient is tin (Sn)is dispersed as a conductive filler in the binder resin is used as thesecond conductive adhesive 20-2. However, the present invention is notlimited to this.

An adhesive where 30 wt % or more of, for example, zinc (Zn), cobalt(Co), iron (Fe), palladium (Pd), platinum (Pt), or an alloy includingthese metals, instead of tin (Sn) or a mixture (intermetallic compound)or an alloy whose main ingredient is tin (Sn), is dispersed in thebinder resin may be used as the second conductive adhesive 20-2. In thiscase, it is possible to achieve the same effect as that explained in theabove discussed example.

In the meantime, in the conductive adhesive 20 having a two-layerstructure formed by the first conductive adhesive 20-1 and the secondconductive adhesive 20-2, the second conductive adhesive 20-2 is formedoutside the first conductive adhesive 20-1 so as to cover the externalcircumferential surface of the first conductive adhesive 20-1. The firstconductive adhesive 20-1 is exposed on the surface where the conductiveadhesive 20 is connected to the bonding electrodes 14 of the wiringboard 11.

This structure is discussed with reference to FIG. 3. Here, FIG. 3 is aview of a conductive adhesive 20 (shown in FIG. 2) seen from an uppersurface side of the bonding electrode 14, namely from a side of asurface where the bonding electrode 14 is connected to the conductiveadhesive 20.

As shown in FIG. 3, the first conductive adhesive 20-1 is exposedsubstantially in the center of the surface where the conducive adhesive20 is connected to the bonding electrode 14 of the wiring board 11 in astate where the first conductive adhesive 20-1 is surrounded by thesecond conductive adhesive 20-2.

Under this structure, even if volume resistivity of the secondconductive adhesive 20-2 where tin (Sn) or mixture (intermetalliccompound) or alloy whose main ingredient is tin (Sn) is dispersed in thebinder resin as the conductive filler is high, since the firstconductive adhesive 20-1 is exposed in the substantially center of thesurface connecting to the bonding electrode 14 of the wiring board 11,it is possible to securely achieve conductivity between the bondingelectrode 14 of the wiring board 11 and the convex shaped outsideconnection terminals 13 of the semiconductor element 12. Here, in thefirst conductive adhesive 20-1, silver (Ag) or a mixture (intermetalliccompound) or an alloy whose main ingredient is silver (Ag) is dispersedas a conductive filler in the above-mentioned binder resin. Silver (Ag)has a low volume resistivity and low contact resistance with gold (Au)forming the convex shaped outside connection terminals 13 of thesemiconductor element 12.

Referring back to FIG. 1, the underfill material 17 which is an adhesivemade of, for example, epoxy resin, polyimide resin, acrylic resin,silicon resin, or another thermosetting insulation resin is suppliedbetween the semiconductor element 12 and the upper surface of the wiringboard 11 by a dispensing method, a printing method, a transferringmethod, or the like. Conductive particles of silver (Ag), solder ornickel (Ni) may be includes in the underfill a material 17.

As discussed above, the semiconductor device 10 of the embodiment of thepresent invention has an arrangement structure of the conductiveadhesive 20 discussed with reference to FIG. 2 and FIG. 3. In addition,in the semiconductor device 10, the semiconductor element 12 is mountedand fixed on the main surface of the wiring board 11 in a flip-chip(face down) state.

Furthermore, the conductive adhesive 20 in this example has a two-layerstructure formed by the first conductive adhesive 20-1 and the secondconductive adhesive 20-2. The conductive adhesive 20 connects the convexshaped outside connection terminals 13 of the semiconductor device 12and the bonding electrodes 14 of the wiring board 11 to each other. Thesecond conductive adhesive 20-2 is formed outside the first conductiveadhesive 20-1 so as to cover the external circumferential surface of thefirst conductive adhesive 20-1. The first conductive adhesive 20-1 isexposed on the surface where the conductive adhesive 20 is connected tothe bonding electrodes 14 of the wiring board 11.

In the first adhesive 20-1, silver (Ag) or a mixture (intermetalliccompound) or an alloy whose main ingredient is silver (Ag) is dispersedas a conductive filler in the binder resin. Silver (Ag) has low contactresistance with gold (Au) forming the convex shaped outside connectionterminals 13 of the semiconductor element 12. Such a first conductiveadhesive 20-1 is exposed substantially in the center of the surfacesconnecting to the bonding electrodes 14 of the wiring board 11.Accordingly, it is possible to securely achieve the conductivity betweenthe convex shaped outside connection terminals 13 of the semiconductorelement 12 and the bonding electrodes 14 of the wiring board 11.

Furthermore, by the oxide film of tin (Sn) formed on the externalsurface of the second conductive adhesive 20-2, it is possible toprevent hydroxide ions (OH⁻) supplied from the wiring board 11 or theunderfill material 17 from being taken into the first conductiveadhesive 20-1 too much.

Accordingly, it is possible to secure high reliability of thesemiconductor device even if a narrow pitch connection of the convexshaped outside connection terminals 13 of the semiconductor elementcannot be avoided. Hence, the embodiment of the present invention cancontribute high functionality to the electronic apparatus where thesemiconductor device is mounted.

[Manufacturing Method of the Semiconductor Device]

Next, manufacturing methods of the semiconductor device of theembodiment of the present invention are discussed. Here, two kinds ofthe methods are discussed.

1. A First Manufacturing Method of the Semiconductor Device

FIG. 4 through FIG. 7 are first through fourth views of the firstmanufacturing method of the semiconductor device of the embodiment ofthe present invention.

In the first manufacturing method of the semiconductor device of theembodiment of the present invention, a flip chip bonder 30 shown in FIG.4( a) is used. The flip chip bonder 30 includes a bonding stage 31, anabsorbing tool 32, a transferring stage 33 (33-1, 33-2), a levelingstage 34, and others. The wiring board 11 is mounted on the bondingstage 31. The absorbing tool 32 applies an attracting force to and holdsthe semiconductor element 12 and carries the semiconductor element 12 ina direction indicated by an arrow in FIG. 4( a). The leveling stage 34is made of glass where, for example, fluororesin is coated.

The inventor of the present invention performed a test of themanufacturing method of the semiconductor device of the embodiment ofthe present invention by using FCB2M made by Panasonic FactoryEngineering as the flip chip bonder 30.

FIG. 4( b) is an expanded view of the semiconductor element 12 held bythe absorbing tool 32. The semiconductor element 12 includes a silicon(Si) semiconductor substrate formed by a known semiconductormanufacturing process. The convex shaped outside connection terminals 13are formed on the outside connection terminal pads 16 of thesemiconductor element 12.

The convex shaped outside connection terminal 13 is formed by, forexample, a so-called ball bonding method using a wire bonding technique.More specifically, a seating part is formed by pressure fixing orconnecting a gold (Au) ball and a projection part projecting from theseating part so that the convex (projection) shaped outside connectionterminal 13 is formed. A flattening process is applied to a top part ofthe projection part of the convex shaped outside connection terminal 13,if necessary.

The inventor of the present invention performed a test of themanufacturing method of the semiconductor device of the embodiment ofthe present invention by using a semiconductor element having arectangular shaped plan configuration of 6.5 mm×6.5 mm, where 360 convexshaped outside connection terminals 13 made of gold (Au) with height of30 μm are formed at a 50 μm pitch on the semiconductor element 12.

The semiconductor element 12 is held by the absorbing tool 32 so thatthe surface of the semiconductor element 12 where the convex outsideconnection terminals 13 are formed faces down and is moved above a firsttransferring stage 33-1 as shown in FIG. 4( c).

The first conductive adhesive 20-1 is coated on the first transferringstage 33-1. The thickness of the first conductive adhesive 20-1 isadjusted by a squeegee (blade) 35-1 which can be moved in a directionindicated by a white arrow in FIG. 4( c) so as to have a designatedthickness such as approximately 10 μm.

As the first conductive adhesive 20-1, an adhesive is used where silver(Ag) or a mixture (intermetallic compound) or an alloy whose mainingredient is silver (Ag) is dispersed as a conductive filler in thebinder resin. Silver (Ag) has a low volume resistivity and low contactresistance with gold (Au) forming the convex shaped outside connectionterminal 13 of the semiconductor element 12. Silver palladium (AgPd),for example, can be used as a mixture (intermetallic compound) or analloy whose main ingredient is silver (Ag). As the binder resin, anepoxy composition, an acrylic composition, a vinyl composition, athermosetting composition such as a composition where a hydroxyl groupis provided at an end, a resin composition soluble in a solvent, amixture of them, or the like can be used. In the epoxy resin as thebinder resin, an epoxy based compound as an epoxy curing agent is anessential ingredient and a surface active agent or flux may be applied.

The inventor of the present invention used an adhesive where silver (Ag)particles having 100 nm average particle diameter are dispersed in epoxyresin (for example, ADEKA HARDNER EH series made by ADEKA), as the firstadhesive 20-1. The inventor of the present invention coated the firstconductive adhesive 20-1 on the first transferring stage 33-1 andadjusted the thickness of the first conductive adhesive 20-1 by usingthe squeegee (blade) 35-1 so that the first conductive adhesive 20-1 hasa thickness of approximately 10 μm.

At this stage, the absorbing tool 32 holding the semiconductor element11 is lowered so that the semiconductor element 11 is pushed onto thefirst transferring stage 33-1 by a load (force) of approximately 4.9 Nand the semiconductor element 11 is dipped in the first conductiveadhesive 20-1. As a result of this, the first conductive adhesive 20-1is transferred to the convex shaped outside connection terminals 13 ofthe semiconductor element 12.

After the first conductive adhesive 20-1 is transferred to the convexshaped outside connection terminals 13 of the semiconductor element 12,the first conductive adhesive 20-1 is heated at, for example, 70 through240° C. by the absorbing tool 32 holding the semiconductor element 12 soas to be provisionally cured.

The inventor of the present invention heated, in this step, the firstconductive adhesive 20-1 at 180° C. for 90 seconds by using theabsorbing tool 32.

After the first conductive adhesive 20-1 is provisionally cured for ashort period of time, in order to improve productivity, as shown in FIG.5( d), the semiconductor element 32 having the convex shaped outsideconnection terminals 13 where the provisionally cured first conductiveadhesive 20-1 is provided is taken so as to be received in an oven 36 ina nitrogen (N₂) environment. In the oven 36, the semiconductor element32 is heated for 60 minutes at approximately 200° C. so that the firstconductive adhesive 20-1 is cured.

The inventor of the present invention performed this heating process inthe oven 36 of the nitrogen (N₂) environment by using an inert oven madeby Yamato Scientific Co., Ltd. for 60 minutes. For example, in a casewhere a conductive adhesive 84-1LMISR$ is used as the first conductiveadhesive 20-1, an elastic modulus after curing is approximately 4 GPa.

For the convenience of explanation, the above-mentioned semiconductorelement 12 is shown in an expanded manner in FIG. 5( d).

Next, the semiconductor element 32 having the convex shaped outsideconnection terminals 13 where the cured first conductive adhesive 20-1is provided is held by the absorbing tool 32 to move above the secondtransferring stage 33-2 with the surface of the semiconductor element 32where the convex shaped outside connection terminals 13 are formedfacing down. This is shown in FIG. 5( e). In FIG. 5( e), for theconvenience of explanation, illustration of the first conductiveadhesive 20-1 formed on the convex shaped outside connection terminals13 is omitted.

The second conductive adhesive 20-2 is coated on the second transferringstage 33-2. The thickness of the second conductive adhesive 20-2 isadjusted by a squeegee (blade) 35-2 which can be moved in a directionindicated by a white arrow in FIG. 5( e) so as to have a designatedthickness such as approximately 15 μm.

As the second conductive adhesive 20-2, an adhesive is used where tin(Sn) or a mixture (intermetallic compound) or an alloy whose mainingredient is tin (Sn) is dispersed as a conductive filler in the binderresin. As the binder resin, an epoxy composition, an acryliccomposition, a vinyl composition, a thermosetting composition such as acomposition where a hydroxyl group is provided at an end, a resincomposition soluble in a solvent, a mixture of them, or the like isused. In the epoxy resin as the binder resin, an epoxy based compound asan epoxy curing agent is an essential ingredient and a surface activeagent or flux may be applied.

An adhesive where 30 wt % or more of, for example, zinc (Zn), cobalt(Co), iron (Fe), palladium (Pd), platinum (Pt), or an alloy includingthese metals, instead of tin (Sn) or a mixture (intermetallic compound)or an alloy whose main ingredient is tin (Sn), is dispersed in thebinder resin may be used as the second conductive adhesive 20-2.

The inventor of the present invention used an adhesive where 30 wt % ormore of tin (Sn) particles having 0.1 nm average particle diameter aredispersed in binder resin as the second adhesive 20-2.

At this stage, the absorbing tool 32 holding the semiconductor element11 is lowered so that the semiconductor element 11 is pushed onto thesecond transferring stage 33-2 by a load of approximately 4.9 N and thesemiconductor element 11 is dipped in the second conductive adhesive20-2. As a result of this, the second conductive adhesive 20-2 istransferred onto the convex shaped outside connection terminals 13 ofthe semiconductor element 12 covered with the first conductive adhesive20-1.

This is shown in FIG. 5( f). At this time, while the first conductiveadhesive 20-1 is cured by the step shown in FIG. 5( d), the secondconductive adhesive 20-2 is not cured but remains a paste. In FIG. 5(f), for the convenience of explanation, the above-discussedsemiconductor element 12 is shown in an expanded manner.

Next, the semiconductor element 32 having the convex shaped outsideconnection terminals 13 where the cured first conductive adhesive 20-1is provided is held by the absorbing tool 32 to move above the levelingstage 34 so that the surface of the semiconductor element 32 where theconvex shaped outside connection terminals 13 are formed faces down. Theabsorbing tool 32 is lowered so that the semiconductor element 11 ispushed onto the leveling stage with a load of approximately 4.9 N orapproximately 0.01 through 10 gf per each the convex shaped outsideconnection terminal 13. This is shown in FIG. 6( g). In FIG. 6( g), forthe convenience of explanation, illustrations of the second conductiveadhesive 20-2 and the first conductive adhesive 20-1 formed on theconvex shaped outside connection terminals 13 are omitted.

The semiconductor element 12 is heated at a designated temperature suchas 50 through 180° C. by the absorbing tool 32 holding the semiconductorelement 12. A leveling process of the second conductive adhesive 20-2transferred to the convex shaped outside connection terminal 13 coveredwith the first conductive adhesive 20-1 is performed, so that an organicsolvent contained in the second conductive adhesive 20-2 is evaporatedand flowing properties of the second conductive adhesive 20-2 arereduced. This is shown in FIG. 6( h). In FIG. 6( h), for the convenienceof explanation, the semiconductor element 12 is shown in an expandedmanner.

The inventor of the present invention performed this leveling process byheating at 120° C. for 30 seconds with the absorbing tool 32.

As shown in FIG. 6( h), by this step, the conductive adhesive 20 has atwo-layer structure formed by the first conductive adhesive 20-1 and thesecond conductive adhesive 20-2. More specifically, a layer formed bythe first conductive adhesive 20-1 is situated around the projectionpart 13-b positioned on the seating part 13-a of the convex shapedoutside connection terminal 13. The second conductive adhesive 20-2 isformed outside the first conductive adhesive 20-1 so as to cover theexternal circumferential surface of the first conductive adhesive 20-1.

Since the second conductive adhesive 20-2 is not cured at this time, asa leveling load is applied in the leveling process, a lower side part (aside of the head end of the convex shaped outside connection terminal13) of the second conductive adhesive 20-2 is moved outside. If anapplied load exceeds a designated force, as show in FIG. 6( i), a lowersurface of the first conductive adhesive 20-1, namely a surface to beconnected to the bonding electrodes 14 of the wiring board 11 in thefollowing step, is exposed so that the first conductive adhesive 20-1 issurrounded by the second conductive adhesive 20-2. Here, FIG. 6( i) is aview of the conductive adhesive 20 where the leveling process isapplied, seen in the direction indicated by an arrow A in FIG. 6( h).

Thus, in the second conductive adhesive 20-2, tin (Sn) or a mixture(intermetallic compound) or an alloy whose main ingredient is tin (Sn)is dispersed as a conductive filler in the binder resin. In addition, asthe first conductive adhesive 20-1, an adhesive is used where silver(Ag) or a mixture (intermetallic compound) or an alloy whose mainingredient is silver (Ag) is dispersed as a conductive filler in thebinder resin. Silver (Ag) has a low volume resistivity and low contactresistance with gold (Au) forming the convex shaped outside connectionterminal 13 of the semiconductor element 12. Even if the volumeresistivity of the second conductive adhesive 20-2 is high, the firstconductive adhesive 20-1 is exposed substantially in the center of thesurface connecting to the bonding electrode 14 of the wiring board 11.Accordingly, in a following step of connecting the semiconductor element12 to the wiring board 11, it is possible to securely achieve electricalconductivity between the convex shaped outside connection terminal 13 ofthe semiconductor element 12 and the bonding electrode 14 of the wiringboard 11.

Next, the convex shaped outside connection terminals 13 of thesemiconductor element 12 having a two-layer structure formed by thefirst conductive adhesive 20-1 and the second conductive adhesive 20-2and the bonding electrodes 14 of the wiring board 11 are connected sothat the semiconductor element 12 and the wiring board 11 are connectedto each other.

As shown in FIG. 7( j), the paste underfill material 17 is applied onthe wiring board 31 mounted and fixed on the bonding stage 31. As theunderfill material 17, epoxy resin, polyimide resin, acrylic resin,silicon resin, or another thermosetting insulation resin may be used.The underfill material 17 may be provided by a dispensing method, aprinting method, a transferring method, or the like. Conductiveparticles made of silver (Ag), solder or nickel (Ni) may be applied tothe underfill material 17.

At this time, the wiring board 11 may be heated at a designatedtemperature by heating the above-mentioned bonding stage. As a result ofthis, the viscosity of the underfill material 17 applied on the wiringboard 11 is reduced so that the flow properties of the underfillmaterial 45 can be improved.

The inventor of the present invention used E-1206 made by Emerson &Cuming as the underfill material 17 for implementing a test of thismanufacturing method.

Next, the absorbing tool 32 (not shown in FIG. 7( j)) holding thesemiconductor element 12 is lowered so that the main surface of thewiring board 11 where the underfill material 17 is applied is parallelwith the main surface of the semiconductor element 12. While heating bythe absorbing tool 32 is maintained, the load is applied so that thesemiconductor element 12 is fixed to the wiring board via the underfillmaterial 17. This is shown in FIG. 7( k). In FIG. 7( k), for theconvenience of explanation, the above-discussed semiconductor element 12is shown in an expanded manner.

For implementing the test of the manufacturing method, the inventor ofthe present invention applied a load of 25.5 N to the bonding electrodes14 of the wiring board 11 where the underfill material 17 is applied andapplied heating at 220° C. for 60 seconds.

As discussed above, in the second conductive adhesive 20-2, tin (Sn) ora mixture (intermetallic compound) or an alloy whose main ingredient istin (Sn) is dispersed as a conductive filler in the binder resin.

Due to heat applied when the convex shaped outside connection terminals13 of the semiconductor element 12 are connected to the bondingelectrodes 14 of the wiring board 11, the second conductive adhesive20-2 takes oxygen (O₂) from the environment so that a thin oxide film isformed on an external surface of the second conductive adhesive 20-2.

Accordingly, even if silver (Ag) or silver contained in a mixture(intermetallic compound) or an alloy whose main ingredient is silver(Ag) is eluted as ions, by the oxide film of tin (Sn) formed on theexternal surface of the second conductive adhesive 20-2, it is possibleto prevent hydroxide ion (OH⁻) supplied from the wiring board 11 or theunderfill material 17 from being taken into the first conductiveadhesive 20-1 too much.

Accordingly, in this example as compared to a case such as the casediscussed in Japanese Patent No. 3409957, where silver (Ag) is formed onthe outermost external circumferential part of the convex shaped outsideconnection terminals of the semiconductor element, it is possible toreduce ratios of a case where silver ions (Ag⁺) and hydroxide ions (OH⁻)are associated with each other. Hence, it is possible to preventdendrite formation causing the ion migration and prevent shorts betweenthe semiconductor element 12 and the wiring board 11 due to ionmigration of silver (Ag).

Thus, the semiconductor element 12 is mounted and fixed on the mainsurface of the wiring board 11 by a flip-chip (face down) method.Furthermore, at least the projection part of the convex shaped outsideconnection terminals 13 of the semiconductor element 12 and the bondingelectrodes 14 on the wiring board corresponding to the projection partsare commonly covered with the conductive adhesive 20 having theabove-mentioned two-layer structure. Thus, at least the projection partof the convex shaped outside connection terminals 13 and the bondingelectrodes 14 are mechanically and electrically connected to each other.

After that, the semiconductor element 12 is released by the absorbingtool 32 and the absorbing tool 32 rises.

Then, outside connecting electrodes 15 such as solder balls made of tin(Sn)—silver (Ag) solder or tin (Sn)—silver (Ag)—copper (Cu) are providedin a grid manner on the rear surface of the wiring board 11 which is thesurface situated opposite to the surface where plural semiconductorelements 12 are mounted.

After that, the wiring board 11 is cut into plural parts where thesemiconductor elements 12 are mounted by using a dicing blade or thelike. As a result of this, the semiconductor device 10 where thesemiconductor element 12 is flip-chip mounted on the wiring board 11 isformed.

If a sealing process is necessary for the semiconductor element 12, forexample, before the wiring board 11 is cut into pieces, a resin sealingprocess is performed on the surface of the wiring board 11 where thesemiconductor elements 12 are mounted. After the resin sealing process,the wiring board 11 and the sealing resin part are cut in the thicknessdirection into parts on each of which a semiconductor element 12 ismounted. Thus, the semiconductor device which is sealed by resin and cutcan be formed.

Thus, the adhesive 20 is provided in the semiconductor device 10 formedby the above-discussed manufacturing method. The adhesive 20 has atwo-layer structure where the second conductive adhesive 20-2 is formedoutside the first conductive adhesive 20-1 so as to cover the externalcircumferential surface of the first conductive adhesive 20-1. The firstconductive adhesive 20-1 is exposed in the surface where the conductiveadhesive 20 is connected to the bonding electrodes 14 of the wiringboard 11. Accordingly, it is possible to securely achieve conductivitybetween the convex shaped outside connection terminals 13 of thesemiconductor element 12 and the bonding electrodes 14 of the wiringboard 11.

In addition, by the oxide film of tin (Sn) formed on the externalsurface of the second conductive adhesive 20-2, it is possible toprevent hydroxide ions (OH⁻) supplied from the wiring board 11 or theunderfill material 17 from being taken into the first conductiveadhesive 20-1 too much. Therefore, it is possible to prevent dendriteformation causing the ion migration and prevent shorts between thesemiconductor element 12 and the wiring board 11 due to ion migration ofsilver (Ag).

Accordingly, it is possible to secure high reliability of thesemiconductor device even if narrow pitch connection of the convexshaped outside connection terminals of the semiconductor element cannotbe avoided. Hence, the embodiment of the present invention cancontribute to high functionality of the electronic apparatus where thesemiconductor device is mounted.

According to the test performed by the inventor of the presentinvention, in the semiconductor device manufactured by the manufacturingmethod of the embodiment of the present invention, it was recognizedthat insulation resistance after 1000 hours passed was equal to orgreater than 1×10¹⁰Ω, the ion migration of silver (Ag) was prevented,and high reliability of the semiconductor device was secured.

Heating conditions such as heating temperature in the present inventionare not limited to the above-discussed example. The heating conditionssuch as heating temperature are properly determined based on materialsof the first conductive adhesive 20-1 and the second conductive adhesive20-2.

2. A Second Manufacturing Method of the Semiconductor Device

FIG. 8 through FIG. 10 are first through third views of the secondmanufacturing method of the semiconductor device of the embodiment ofthe present invention.

In the second manufacturing method of the semiconductor device of theembodiment of the present invention, the flip chip bonder 30 (see FIG.4( a)) used in the above-discussed first manufacturing method is used.In the second manufacturing method unlike the first manufacturingmethod, the leveling stage 34 is not used.

The inventor of the present invention performed a test of the secondmanufacturing method of the semiconductor device of the embodiment ofthe present invention by using FCB2M made by Panasonic FactoryEngineering as the flip chip bonder 30.

FIG. 8( a) is an expanded view of the semiconductor element 12 held bythe absorbing tool 32. The semiconductor element 12 includes a silicon(Si) semiconductor substrate formed by a known semiconductormanufacturing process. The convex shaped outside connection terminals 13are formed on the outside connection terminal pads 16 of thesemiconductor element 12.

The convex shaped outside connection terminal 13 is formed by, forexample, a so-called ball bonding method using a wire bonding technique.More specifically, a seating part is formed by pressure fixing orconnecting a gold (Au) ball and a projection part projecting from theseating part so that the convex (projection) shaped outside connectionterminal 13 is formed. A flattening process is applied to a top part ofthe projection part of the convex shaped outside connection terminal 13,if necessary.

The inventor of the present invention performed a test of themanufacturing method of the semiconductor device of the embodiment ofthe present invention, by using a semiconductor element having arectangular shaped plan configuration of 6.5 mm×6.5 mm and where 360convex shaped outside connection terminals 13 made of gold (Au) withheight of 30 μm are formed at 50 μm pitch, as the semiconductor element12.

The semiconductor element 12 is held by the absorbing tool 32 so thatthe surface of the semiconductor element 12 where the convex outsideconnection terminals 13 are formed is faced down and is moved above afirst transferring stage 33-1. This is shown in FIG. 8( b).

The first conductive adhesive 20-1 is coated on the first transferringstage 33-1. The thickness of the first conductive adhesive 20-1 isadjusted by a squeegee (blade) 35-1 which can be moved in a directionindicated by a white arrow in FIG. 4( c) so as to have a designatedthickness such as approximately 10 μm.

As the first conductive adhesive 20-1, an adhesive is used where silver(Ag) or a mixture (intermetallic compound) or an alloy whose mainingredient is silver (Ag) is dispersed as a conductive filler in thebinder resin. Silver (Ag) has a low volume resistivity and low contactresistance with gold (Au) forming the convex shaped outside connectionterminal 13 of the semiconductor element 12. Silver palladium (AgPd),for example, can be used as a mixture (intermetallic compound) or analloy whose main ingredient is silver (Ag). As the binder resin, anepoxy composition, an acrylic composition, a vinyl composition, athermosetting composition such as a composition where a hydroxyl groupis provided at an end, a resin composition soluble in a solvent, amixture of them, or the like can be used. In the epoxy resin as thebinder resin, an epoxy based compound as an epoxy curing agent is anessential ingredient and a surface active agent or flux may be applied.

The inventor of the present invention used an adhesive where silver (Ag)particles having 100 nm average particle diameter are dispersed in epoxyresin (for example, ADEKA HARDNER EH series made by ADEKA), as the firstadhesive 20-1. The inventor of the present invention coated the firstconductive adhesive 20-1 on the first transferring stage 33-1 andadjusted the thickness of the first conductive adhesive 20-1 with thesqueegee (blade) 35-1 so that the first conductive adhesive 20-1 has athickness of approximately 10 μm.

At this stage, the absorbing tool 32 holding the semiconductor element11 is lowered so that the semiconductor element 11 is pushed onto thefirst transferring stage 33-1 by a force of approximately 4.9 N and thesemiconductor element 11 is dipped in the first conductive adhesive20-1. As a result of this, the first conductive adhesive 20-1 istransferred onto the convex shaped outside connection terminal 13 of thesemiconductor element 12.

After the first conductive adhesive 20-1 is transferred onto the convexshaped outside connection terminal 13 of the semiconductor element 12,the first conductive adhesive 20-1 is heated at, for example, 70 through240° C., by the absorbing tool 32 holding the semiconductor element 12so as to be provisionally cured. The inventor of the present inventionheated, in this step, the first conductive adhesive 20-1 at 180° C. for90 seconds by using the absorbing tool 32.

After the first conductive adhesive 20-1 is provisionally cured for ashort period of time, in order to improve productivity, as shown in FIG.8( c), the semiconductor element 32 having the convex shaped outsideconnection terminals 13 where the provisionally cured first conductiveadhesive 20-1 is provided is taken so as to be received in an oven 36 ina nitrogen (N₂) environment. In the oven 36, the semiconductor element32 is heated for 60 minutes at approximately 200° C. so that the firstconductive adhesive 20-1 is cured.

The inventor of the present invention performed this heating process inthe oven 36 with the nitrogen (N₂) environment by using an inert ovenmade by Yamato Scientific Co., Ltd. for 60 minutes. For example, in acase where a conductive adhesive 84-1LMISR$ is used as the firstconductive adhesive 20-1, its elastic modulus after curing isapproximately 4 GPa.

For the convenience of explanation, the above-mentioned semiconductorelement 12 is shown in an expanded manner in FIG. 8( c).

Next, the semiconductor element 12 having the convex shaped outsideconnection terminals 13 where the cured first conductive adhesive 20-1is provided is held by the absorbing tool 32 to move above the secondtransferring stage 33-2 so that the surface of the semiconductor element32 where the convex shaped outside connection terminals 13 are formedfaces down. This is shown in FIG. 9( d). In FIG. 9( d), for theconvenience of explanation, illustration of the first conductiveadhesive 20-1 formed on the convex shaped outside connection terminals13 is omitted.

The second conductive adhesive 20-2 is coated on the second transferringstage 33-2. The thickness of the second conductive adhesive 20-2 isadjusted by a squeegee (blade) 35-2 which can be moved in a directionindicated by a white arrow in FIG. 5( d) so as to have a designatedthickness such as approximately 15 μm.

As the second conductive adhesive 20-2, an adhesive is used tin (Sn) ora mixture (intermetallic compound) or alloy whose main ingredient is tin(Sn) is dispersed as a conductive filler in the binder resin. As thebinder resin, an epoxy composition, an acrylic composition, a vinylcomposition, a thermosetting composition such as a composition where ahydroxyl group is provided at an end, a resin composition soluble in asolvent, a mixture of them, or the like may be used. In the epoxy resinas the binder resin, an epoxy based compound as an epoxy curing agent isan essential ingredient and a surface active agent or flux may beapplied.

An adhesive where 30 wt % or more of, for example, zinc (Zn), cobalt(Co), iron (Fe), palladium (Pd), platinum (Pt), or an alloy includingthese metals, instead of tin (Sn) or a mixture (intermetallic compound)or an alloy whose main ingredient is tin (Sn), is dispersed in thebinder resin may be used as the second conductive adhesive 20-2.

The inventor of the present invention used an adhesive where 30 wt % ormore of rate of tin (Sn) particles having 0.1 nm of average particlediameter are dispersed in binder resin, as the second adhesive 20-2.

At this stage, the absorbing tool 32 holding the semiconductor element12 is lowered so that the semiconductor element 12 is pushed onto thesecond transferring stage 33-2 by a load of approximately 4.9 N and thesemiconductor element 12 is dipped in the second conductive adhesive20-2. As a result of this, the second conductive adhesive 20-2 istransferred onto the convex shaped outside connection terminals 13 ofthe semiconductor element 12 covered with the first conductive adhesive20-1.

This is shown in FIG. 9( e). At this time, while the first conductiveadhesive 20-1 cured by the step shown in FIG. 8( c), the secondconductive adhesive 20-2 is not cured but remains a paste state. In FIG.9( e), for the convenience of explanation, the above-discussedsemiconductor element 12 is shown in an expanded manner.

Next, the convex shaped outside connection terminals 13 of thesemiconductor element 12 where the first conductive adhesive 20-1 coversand the second conductive adhesive 20-2 is transferred is connected tothe bonding electrodes 14 of the wiring board 11, so that thesemiconductor element 12 is connected to the wiring board 11.

More specifically, the absorbing tool 32 holding the semiconductorelement 12 is lowered so that the main surface of the wiring board 11mounted on the bonding stage 31 is parallel with the main surface of thesemiconductor element 12.

While heating by the absorbing tool 32 is maintained, the load isapplied so that the semiconductor element 12 is mounted on the wiringboard 11. This is shown in FIG. 9( f). In FIG. 9( f), for theconvenience of explanation, the above-discussed semiconductor element 12is shown in an expanded manner.

At this time, the wiring board 11 may be heated at a designatedtemperature by heating the above-mentioned bonding stage 32. As a resultof this, the viscosity of the underfill material 17 applied on thewiring board 11 in the following steps is reduced so that the flowproperties of the underfill material 45 can be improved.

For implementing the test of the manufacturing method, the inventor ofthe present invention set the heating temperature of the absorbing tool32 to 40° C. and applied a load of 4.9 N to the bonding electrodes 14 ofthe wiring board 11 for 10 seconds. Then, the inventor of the presentinvention applied a load of 24.5 N and heated at 220° C. for 60 seconds.

As discussed above, in the second conductive adhesive 20-2, tin (Sn) ora mixture (intermetallic compound) or an alloy whose main ingredient istin (Sn) is dispersed as a conductive filler in the binder resin.

Due to heat applied when the convex shaped outside connection terminals13 of the semiconductor element 12 are connected to the bondingelectrodes 14 of the wiring board 11, the second conductive adhesive20-2 takes oxygen (O₂) from the environment so that a thin oxide film isformed on an external surface of the second conductive adhesive 20-2.

Accordingly, even if silver (Ag) or silver contained in a mixture(intermetallic compound) or an alloy whose main ingredient is silver(Ag) is eluted as ions, by the oxide film of tin (Sn) formed on theexternal surface of the second conductive adhesive 20-2, it is possibleto prevent a hydroxide ions (OH⁻) supplied from the wiring board 11 orthe underfill material 17 from being taken into the first conductiveadhesive 20-1 too much. Accordingly, in this example as compared to acase, such as a case discussed in Japanese Patent No. 3409957, wheresilver (Ag) is formed on the outermost external circumferential part ofthe convex shaped outside connection terminal of the semiconductorelement, it is possible to reduce ratios of a case where silver ions(Ag⁺) and a hydroxide ions (OH⁻) are associated with each other. Hence,it is possible to prevent dendrite formation causing the ion migrationand prevent shorts between the semiconductor element 12 and the wiringboard 11 due to ion migration of silver (Ag).

In the case of the bonding electrodes 14 of the wiring board 11 and theconvex shaped outside connection terminals 13 which are covered with thefirst conductive adhesive 20-1 and to which the second conductiveadhesive 20-2 is transferred, the second conductive adhesive 20-2 is notcured. Accordingly, as the load from the absorbing tool 32 is appliedfor connecting, a lower side part of the second conductive adhesive 20-2(situated at the head end of the convex shaped outside connectionterminals 13) is moved outside. When the applied load exceeds thedesignated load, as shown in FIG. 10( g), a lower surface of the firstconductive adhesive 20-1, namely the surface to be connected to thebonding electrodes 14 of the wiring board 11 in the following step, isexposed in a state where the first conductive adhesive 20-1 issurrounded by the second conductive adhesive 20-2. Here, FIG. 10( g) isa view of the conductive adhesive 20 shown in FIG. 9( f) seen from anupper surface side of the bonding electrodes 14, namely the surfacewhere the bonding electrodes 14 are connected to the conductive adhesive20.

Thus, in the second conductive adhesive 20-2, tin (Sn) or a mixture(intermetallic compound) or an alloy whose main ingredient is tin (Sn)is dispersed as a conductive filler in the binder resin. In addition, asthe first conductive adhesive 20-1, an adhesive is used where silver(Ag) or a mixture (intermetallic compound) or an alloy whose mainingredient is silver (Ag) is dispersed as a conductive filler in thebinder resin. Silver (Ag) has a low volume resistivity and low contactresistance with gold (Au) forming the convex shaped outside connectionterminal 13 of the semiconductor element 12. Even if the volumeresistivity of the second conductive adhesive 20-2 is high, the firstconductive adhesive 20-1 is exposed in substantially the center of thesurface connecting to the bonding electrodes 14 of the wiring board 11.Accordingly, in a following step of connecting the semiconductor element12 to the wiring board 11, it is possible to securely achieve electricalconductivity between the convex shaped outside connection terminals 13of the semiconductor element 12 and the bonding electrode 14 of thewiring board 11.

After that, as shown in FIG. 10( h), the paste underfill material 17 isapplied between the semiconductor element 12 and the wiring board 11mounted and fixed on the bonding stage 31 by the dispenser 37. As theunderfill material 17, epoxy resin, polyimide resin, acrylic resin,silicon resin, or another thermosetting insulation resin may be used.Conductive particles made of silver (Ag), solder or nickel (Ni) may beincludes in the underfill a material 17.

The inventor of the present invention supplied E-1206 made by Emerson &Cuming as the underfill material 17 between the wiring board 11 and thesemiconductor element 12, heated this in the oven under the nitrogen(N₂) atmosphere at 150° C. for one hour so that the underfill material17 was cured.

Thus, the semiconductor element 12 is mounted and fixed on the mainsurface of the wiring board 11 by a flip-chip (face down) method.Furthermore, at least the projection part of the convex shaped outsideconnection terminals 13 of the semiconductor element 12 and the bondingelectrode 14 on the wiring board 11 corresponding to the projectionparts are commonly covered with the conductive adhesive 20 having theabove-mentioned two-layer structure. Thus, at least the projection partof the convex shaped outside connection terminals 13 and the bondingelectrodes 14 are mechanically and electrically connected to each other.After that, the semiconductor element is released by the absorbing tool32 and the absorbing tool 32 rises.

Then, outside connecting electrodes 15 such as solder balls made of tin(Sn)—silver (Ag) solder or tin (Sn)—silver (Ag)—copper (Cu) are providedin a grid manner on the rear surface of the wiring board 11 which is asurface situated opposite to the surface where plural semiconductorelements 12 are mounted.

After that, the wiring board 11 is cut into plural parts where thesemiconductor elements 12 are mounted by using a dicing blade or thelike. As a result of this, the semiconductor device 10 where thesemiconductor element 12 is flip-chip mounted on the wiring board 11 isformed.

If a sealing process is necessary for the semiconductor element 12, forexample, before the wiring board 11 is cut into pieces, a resin sealingprocess is performed to the surface of the wiring board 11 where thesemiconductor element 12 is mounted. After the resin sealing process isperformed, the wiring board 11 and the sealing resin part are cut in thethickness direction into parts where the semiconductor elements 12 aremounted. Thus, the semiconductor devices which are sealed by resin andcut can be formed.

Thus, the adhesive 20 is provided in the semiconductor device 10 formedby the above-discussed manufacturing method. The adhesive 20 has atwo-layer structure where the second conductive adhesive 20-2 is formedoutside the first conductive adhesive 20-1 so as to cover the externalcircumferential surface of the first conductive adhesive 20-1. The firstconductive adhesive 20-1 is exposed on the surface where the conductiveadhesive 20 is connected to the bonding electrodes 14 of the wiringboard 11. Accordingly, it is possible to securely achieve conductivitybetween the convex shaped outside connection terminals 13 of thesemiconductor element 12 and the bonding electrodes 14 of the wiringboard 11.

In addition, by the oxide film of tin (Sn) formed on the externalsurface of the second conductive adhesive 20-2, it is possible toprevent hydroxide ion (OH⁻) supplied from the wiring board 11 or theunderfill material 17 from being taken into the first conductiveadhesive 20-1 too much. Therefore, it is possible to prevent dendriteformation causing the ion migration and prevent shorts between thesemiconductor element 12 and the wiring board 11 due to ion migration ofsilver (Ag).

Accordingly, it is possible to secure high reliability of thesemiconductor device even if narrow pitch connection of the convexshaped outside connection terminals of the semiconductor element cannotbe avoided. Hence, the embodiment of the present invention cancontribute to high functionality of the electronic apparatus where thesemiconductor device is mounted.

According to the test performed by the inventor of the presentinvention, in the semiconductor device manufactured by the manufacturingmethod of the embodiment of the present invention, it was recognizedthat insulation resistance after 1000 hours passed was equal to orgreater than 1×10¹⁰Ω, the ion migration of silver (Ag) was prevented,and high reliability of the semiconductor device was secured.

Heating conditions such as heating temperature in the present inventionare not limited to the above-discussed example. The heating conditionssuch as heating temperature are properly determined based on materialsof the first conductive adhesive 20-1 and the second conductive adhesive20-2.

Although the invention has been described with respect to specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teachings hereinset forth.

This patent application is based on Japanese Priority Patent ApplicationNo. 2007-52788 filed on Mar. 2, 2007, the entire contents of which arehereby incorporated by reference.

1. A semiconductor device where an outside connection terminal of asemiconductor element and an electrode of a wiring board are connectedto each other via a conductive adhesive, the conductive adhesivecomprising: a first conductive adhesive provided around the outsideconnection terminal; and a second conductive adhesive formed outside thefirst conductive adhesive and in contact with the outside connectionterminal and the electrode; wherein the first conductive adhesivecontains a conductive filler including silver (Ag), and the secondconductive adhesive contains a conductive filler including a metalselected from a group consisting of tin (Sn), zinc (Zn), cobalt (Co),iron (Fe), palladium (Pd), and platinum (Pt).
 2. The semiconductordevice as claimed in claim 1, wherein the second conductive adhesivefurther contains resin.
 3. The semiconductor device as claimed in claim1, wherein the first conductive adhesive is directly connected to theelectrode of the wiring board.
 4. The semiconductor device as claimed inclaim 1, wherein the conductive filler of the first conductive adhesiveis silver (Ag) or a mixture or an alloy containing silver (Ag).
 5. Thesemiconductor device as claimed in claim 1, wherein the conductivefiller of the second conductive adhesive is tin (Sn) or a mixture or analloy containing tin (Sn).
 6. The semiconductor device as claimed inclaim 2, wherein the resin is made of a material selected from a groupconsisting of an epoxy composition, an acrylic composition, a vinylcomposition, and a thermosetting composition.
 7. The semiconductordevice as claimed in claim 1, further comprising: an underfill materialto a gap between the semiconductor element and the wiring board.
 8. Thesemiconductor device as claimed in claim 7, wherein the underfillmaterial is made of a material selected from a group consisting of epoxyresin, polyimide resin, acrylic resin, and silicon resin.